Method of manufacturing magnetic mass cores



March 7, 1950 J. A. M. SMELT METHOD OF MANUFACTURING MAGNETIC MASS CORES Filed Sept. 19, 1945 JOAEPHUMNIQNMSMARLMMELT IN V EN TOR. BY

ATTORNH.

Patented Mar. 7, 1950 2,499,789

METHOD OF MANUFACTURING MAGNETIC MASS CORES Josephus Antonius Maria Smelt, Eindhoven, Netherlands, assignor to Hartford National Bank 8: Trust 00., Hartford, Conn., as trustee Application September 19, 1945, Serial No. 617,453 In the Netherlands June 16, 1942 a Section 1, Public Law 690, August 8, 1946 Patent expires June 16, 1962 7 Claims. 1

It is known to manufacture magnetic mass cores, for example for radio and telephony purposes, by moulding, if necessary with the aid of a binding agent, a finely divided magnetic metal powder in a matrix at high pressure and, if desired, at increased temperature to form the shape of core desired.

It is further known to form a core by moulding powdery magnetic insulating materials, as magnetain a uniformly magnetic structure throughout their length.

According to the invention, it has further been found that a mixture of oxides of the kind as is ordinarily used for the chemical preparation of a magnetic ferrite is very suitable to be moulded by means of an extrusion press. This fact is taken into account in one embodiment of the invention in which a powdery mixture of oxides tite or other ferrites, for example copper 10 additioned by an organic binding agentismouldferrite, with the aid of a binding agent in a ed with the aid of an extrusion press to form a matrix. For the chemical preparation of these string of the desired section of core, after which ferrites a mixture of the oxides constituting the a heating takes place, during which the mixture ferrite is usually compressed to form a block or of oxides changes into the corresponding maga rod, the compressed mixture of oxides being netic product. sintered until it has changed to ferrite, where- Relatively to the method of manufacture in after puiverisation takes place. which the completed magnetic product previous- Another method of manufacturing magnetic ly sintered is moulded, the above-mentioned specores consists in extrusion moulding in a matrix cial method offers the advantage that a mixture 8. mixture of a powder of magnetic material with of oxides is softer than the sintered product, a binding agent which is fiuid under the influence which is of importance for moulding. Another of heat and solidifies during cooling down in the advantage consists in that the shaping of the trix, core and the chemical preparation of the mag- The present invention relates to a method of netisable product are in this case combined in manufacturing magnetic mass cores, which is one operation in contradistinction to the firstsuperior to all previous methods as regards simmentioned method of manufacture in which a plicity and quickness of manufacture. It relates magnetic product prepared in a special chemimore particularly to a method of manufacturing cal process is moulded to form a core and sintered. mass cores which comprise ferrite as a magnetis- This means a considerable simplification, since able material. now only one heating takes place and only the According to the invention, the shaping of soft mixture of oxides has to be ground, the such cores is effected with the aid of an extrugrinding of the harder product specially manusion press and for the purpose of obtaining factured, which grinding takes much time, besufflcient coherence of the extruded material, the ing suppressed, material to be pressed is additioned by an organic For completeness sake it is mentioned that bindin a n r a ad s as potato flour. the mixture of oxides, which may also contain wheat flour, tragacanth, nitrocellulose. hydroxides, which is used as a primary material It is thus possible, for example, f a p wd ry in the chemical preparation of a magnetic ferrite, ferrite additioned by an or a binder to be may be either of a. stochiometrical composition mould y means of an extrusion Press to form 40 or of a composition different therefrom; the a string of the desired section of core and for the ferrioxide or hydroxide may in this case be mixed string to be cut into pieces and Subsequently either with a simple metallic oxide or with a heated until the ferrite particles Sintel tegethermixture of several metallic oxides. It is also Since durin h he the Organic binding possible to substitute aluminium oxide or agent is exp ll the materiel after the heating chromium oxide for part of the ferrioxyde whilst contains no fo n non-magnetic Substances retaining the ferrite crystal structure of the which might impair the permeability of the core. sintered magnetic t,

Cores thus manufactured, which may be either The following examme describes t manuhollow or solid and may xhi a circul r, reefacture of a magnetic core constituted by a al' 0 any other Section, are of a un mixed copper-zinc ferrite. As a rule, mixtures structure. If desired, they may be subsequently cores for which it was hitherto diflicult to obof oxides which are constituted by ferrioxide, zinc oxide and one or a plurality of other oxides and which change into a mixed zinc ferrite during sintering may be excellently moulded by means of an extrusion press.

Example 250 g. of a mixture composed of mol. per cent of copper oxide, mol. per cent of zinc oxide and 50 mol. per cent of ferrioxide are mixed with 45 g. of a solution of 18% by 'weight of nitrocellulose in a solvent composed of 50 parts of butyl acetate, 25 parts of butanol and 15 parts of ethyl glycol. With the aid of an extrusion press the mixture is moulded to form a tube having an external diameter of 4.8 mms. and an internal diameter of 2.5 mms. After sintering during 2 hours at 1150 C., a magnetic tubular core of copper-zinc ferrite is obtained having an external and an internal diameter of 4 mms. and 2 mms. respectively.

In order that the invention can be more readily understood and carried into effect it will now be described with reference to the accompanying drawing in which an extrusion mold for extruding a core according to the invention is illustrated.

Referring more particularly to the figure, an extrusion mold I is adapted to hold a mixture of ferrite material and an organic binding agent 2 extrudes a compact core 3 through a reduced portion of the mold 4 when plunger 5 compresses the mixture 2.

What I claim is:

1. The method of manufacturing a ferromagnetic core comprising the steps of adding an organic binder to powdered ferrite-forming constituents, extruding the ferrite-forming constituents containing the organic binder to form a core, and sintering said core at a temperature of about 1150 C. to form a mixed ferrite and to expel said binder and form a compact core of ferrite material.

2. The method of manufacturing a ferromagnetic core comprising the steps of, mixing a powdered metallic oxide, powdered zinc oxide, and powdered iron oxide, adding an organic binder to said powdered oxide, extruding the oxide mixture containing the organic binder to form a core, and sintering said core at a temperature of about 1150 C. to form a mixed ferrite and to expel said binder.

3. The method of manufacturing a ferromagnetic core comprising the steps of, adding potato flour to powdered metal oxide ferrite-forming constituents, extruding the oxide constituents containing potato flour to form a core, and sintering said core at a temperature of about 1150 C. to form a mixed ferrite and to expel the potato flour.

4. The method of manufacturing a ferromagnetic core comprising the steps of, adding wheat flour to powdered metal oxide ferrite-formin constituents, extruding the oxide constituents containing wheat flour to form a core, and sintering said core at a temperature of about l150 g. to form a mixed ferrite and to expel the wheat our.

5. The method of manufacturing a ferromagnetic core comprising the steps of, adding tragacanth to powdered metal oxide ferrite-forming constituents, extruding the oxide constituents containing tragacanth to form a core, and sintering said core at a temperature of about 1150 C. to form a mixed ferrite and to expel the tragacanth.

6. The method of manufacturing a ferromagnetic core comprising the steps of, adding nitrocellulose to powdered metal oxide ferrite-forming constituents, extruding the oxide constituents containing nitrocellulose to form a core, and sintering said core at a temperature of about 1150" C. to form a mixed ferrite and to expel the nitrocellulose.

7. The method of manufacturing a ferromagnetic core comprising the steps of, mixing powdered copper oxide, powdered zinc oxide, and powdered iron oxide, in approximate molecular percentages of 20:30:50 respectively, adding a solution of 18% of weight of nitrocellulose in a solvent of butyl acetate, butanol, and ethyl gly- 001 in the approximate ratio of :25:15 to said powdery mixture, extruding said powdery mixture containing nitrocellulose in said solvent to form a core, and heating said core at a temperature of approximately 1150" for approximately 2 hours to form a mixed copper-zinc ferrite and to expel said nitrocellulose and said solvent.

JOSEPHUS ANTONIUS MARIA SMELT.

REFERENCES CITED The following references are of record in the file of this patent:

UNITED STATES PATENTS Number Name Date 1,292,206 Woodruflf Jan. 21, 1919 1,669,548 Elmen May 15, 1928 1,669,646 Bandur May 15, 1928 1,807,915 Iredell June 2, 1931 1,899,584 Novias Feb. 28, 1933 1,904,273 Crowley Apr. 18, 1933 1,946,964 Cobb Feb. 13, 1934 2,031,129 Reichmann Feb. 18, 1936 2,134,752 Ehlers Nov. 1, 1938 

